1. Field of the Invention
The present invention relates generally to the structure and use of radiofrequency electrosurgical apparatus for the treatment of solid tissue. More particularly, the present invention relates to an electrosurgical system having pairs of electrode arrays which are deployed to treat large volumes of tissue, particularly for the treatment of tumors in the liver and other tissues and organs.
The delivery of radiofrequency energy to treatment regions within solid tissue is known for a variety of purposes. Of particular interest to the present invention, radiofrequency energy may be delivered to diseased regions in target tissue for the purpose of causing tissue necrosis. For example, the liver is a common depository for metastases of many primary cancers, such as cancers of the stomach, bowel, pancreas, kidney, and lung. Electrosurgical probes for deploying multiple electrodes have been designed for the treatment and necrosis of tumors in the liver and other solid tissues. See, for example, the LeVeen(trademark) Needle Electrode available from Radio Therapeutics Corporation which is constructed generally in accord with published PCT application WO 98/52480.
The probes described in WO 98/52480 comprise a number of independent wire electrodes which are extended into tissue from the distal end of a cannula. The wire electrodes may then be energized in a monopolar or bipolar fashion to heat and necrose tissue within a defined generally spherical volumetric region of target tissue. In order to assure that the target tissue is adequately treated and to limit damage to adjacent healthy tissues, it is desirable that the array formed by the wire electrodes within the tissue be precisely and uniformly defined.
Despite the significant success that has accompanied use of the LeVeen(trademark) Needle Electrode in treating solid tissue tumors, the ability to treat particular types of tumors has been somewhat limited. For example, the ability to produce very large tissue lesions, for example lesions having volumes greater than 30-35 cm3, has been problematic. In addition, such larger tumors tend to be less spheroidal in shape than smaller tumors. Since the LeVeen(trademark) Needle Electrode produces generally spheroidal lesions, the ability to treat larger, non-spheroidal tumors can be limited. Additionally, the ability to treat highly vascularized tissues and/or tissue near a large blood vessel has also been limited. In the latter cases, heat being introduced by the electrode can be rapidly carried away by circulating blood, making uniform heating and control of temperature in the vascularized tissues difficult. Uniform heating and temperature control of the tissue being treated is, of course, one prerequisite to obtaining homogenous lesions in and around the tumors.
The ability to provide uniform heating and the creation of homogenous tissue lesions is particularly difficult with bipolar devices. The two bipolar electrodes may be placed in regions with quite different perfusion characteristics, and the heating around each pole can be quite different. That is, one pole may be located adjacent to a large blood vessel, while the other pole may be located adjacent to tissue which is less perfused. Thus, the pole located in the less perfused tissue will heat the tissue immediately surrounding the electrode much more rapidly than the tissue surrounding the opposite polar electrode is heated. In such circumstances, the tissue surrounding one pole may be preferentially heated and necrosed, while the tissue surrounding the other pole will neither be heated nor necrosed sufficiently.
For all these reasons, it would be desirable to provide improved electrosurgical methods and systems for treating tumors in the liver and other body organs. It would be particularly desirable if the methods and systems could produce relatively large lesions (regions of necrosed tissue) within the solid tissue, preferably being capable of producing lesions having volumes greater than 30-35 cm3, more preferably greater than 70 cm3, and even more preferably greater than 150 cm3, or larger. In addition, it would be desirable to provide methods and systems which can uniformly produce tissue lesions in highly vascularized tissues, such as the liver, and even more particularly in tissues which are unevenly perfused, such as tissues which are near major blood vessels, in such organs. It would be still further desirable to provide methods and systems which can produce tissue lesions having a variety of geometries, such as ovoid and cylindrical, rather than just spheroidal. At least some of these objectives will be met by the invention of the present application.
2. Description of the Background Art
U.S. Pat. Nos. 5,827,276; 5,855,576; and 5,868,740 to LeVeen and German Patent Publication No. 2124684 to Stadelmayr describe devices for deploying pairs of axially spaced-apart electrode arrays. U.S. Pat. Nos. 6,090,105; 6,071,280; 5,928,229; 5,913,855; 5,863,290; 5,672,174; and 5,672,173, describe multiple electrode devices having coaxial electrode structures including a primary antenna and at least one curved secondary antenna that deploys from the primary antenna. See, also U.S. Pat. No. 5,611,803 and WO 99/32041.
The present invention provides improved methods, apparatus, and kits for performing electrosurgical treatment of tissues and in particular for performing radiofrequency tissue necrosis for the treatment of tumors and diseased tissues. The methods, apparatus, and kits are particularly useful for creating large volume tissue lesions, such as those having volumes above 30 cm3, often above 70 cm3, and sometimes above 150 cm3, or larger. In addition to being able to form relatively large volume tissue lesions, the methods, apparatus, and kits of the present invention are capable of producing highly uniform lesions where tissue necrosis is induced substantially uniformly through the entire treated region. Moreover, the present invention produces lesions having well defined peripheries, typically ovoid or cylindrical, so that targeted tissue having different (non-spherical) geometries) may be necrosed with only minimum damage to adjacent healthy tissues.
In a first aspect of the present invention, probes for deploying electrode arrays comprise a shaft having a distal end and proximal end. A first array of electrodes is mounted on the shaft and is constructed or adapted to shift between a retracted configuration, typically within the shaft, and deployed configuration. The deployed configuration of the first electrode array will have a concave face, typically comprising a plurality of curved electrodes, more typically comprising at least three curved electrodes which evert when deployed from the shaft so that the electrodes each extend generally axially from the shaft, turn radially outward, and preferably turn around so that the tips of the electrodes are turned backwardly relative to their initial direction. In the most preferred embodiments, the electrode array will turn substantially completely, i.e., at or close to 180xc2x0, from the initial axial direction. The probe further includes a second electrode array having electrodes mounted on the shaft at a location spaced-apart proximally from the first array of electrodes. The electrodes of the second array are also capable of shifting between a retracted configuration and a deployed, where the deployed array typically comprises a plurality of everting electrodes, generally as described above. The first and second arrays, when deployed, are arranged so that the concave faces are opposed to each other on opposite sides of a treatment region.
In various preferred embodiments of the apparatus of the present invention, the probe may further include a self-penetrating tip, usually at the distal end of the shaft. The self-penetrating tip can take any conventional form, such as a sharpened tip, an electrosurgical tip (one adapted to penetrate tissue when connected to an electrosurgical power supply operating in a cutting mode), and the like. Alternatively, the probes may be introduced through or by exchange with a conventional cannula and stylet assembly as described generally in U.S. Pat. No. 5,827,276, the full disclosure of which is incorporated herein by reference.
The first and second electrode arrays will be mechanically coupled to the shaft to permit their deployment relative to the shaft. Usually, one electrode array will be mounted to extend in a distal direction and to evert from the shaft while the second array will be mounted to advance in a proximal direction relative to the shaft and to evert therefrom. Usually, the individual electrodes of each electrode array will be received within one or more cavities or lumens within the shaft so that the electrodes may be fully retracted into the shaft for introduction of the probe into tissue and removal of the probe from tissue. Operation of the two arrays may be coupled so that said arrays deploy simultaneously. More usually, however, the arrays will be separately deployable.
The first and second electrode arrays will each be connected or coupled to deployment mechanism(s) for advancing the electrodes relative to the shaft to achieve the desired everted deployment. Usually, the deployment mechanisms will comprise a first rod connected to the first electrode array and slidably disposed in or on the shaft and a second rod or tube connected to the second electrode array and slidably disposed in or on the shaft. In this way, distal advancement of the first rod or tube relative to the shaft causes the first electrode array to extend distally and evert radially outwardly relative to the shaft. Likewise, proximal retraction of the second rod relative to the shaft causes the second electrode array to draw proximally and evert radially outwardly from the shaft. Operation of the first and second rods or tubes may be coupled so that the user need perform only one deployment action using the probe. Usually, however, actuation of the two rods will not be coupled so that deployment of the two electrode arrays may be effected entirely separately. In particular embodiments, the first rod may be mounted coaxially within a central lumen or passage of a second tube to provide for a more compact design.
In a first exemplary embodiment, the first and second rods are mounted coaxially and threaded drive pins are mounted in a handle assembly in order to effect simultaneous advancement and retraction of the first and second rods. In a second exemplary embodiment, the first and second rods are mounted in parallel and a rack and pinion assembly is provided in a handle to effect simultaneous advancement and retraction of the rods. In a third exemplary embodiment, the distal and proximal arrays may be separately advanced, with one array being initially deployed and the second array being separately deployed, usually after the first array is satisfactorily located. Optionally, the electrode deployment device embodiments which permit separate array deployment could be used with only a single array, usually but not necessarily the distal array. While the distal array will normally be deployed first, there is no reason why the proximal array could not be deployed first, with or without subsequent deployment of the distal array. When only one array is deployed, the device could be used in a monopolar fashion with the deployed array being coupled to one pole of the power supply and a second, dispersive electrode (typically placed on an exterior body surface) being coupled to the other pole of the power supply. In the illustration of the third embodiment, the distal array is deployed by advancing a rod which extends axially through the length of the device, typically by depressing a knob at the proximal end of the device. The proximal array, in contrast, is separately deployed by rotating a threaded sleeve in the device, typically using the same knob which is used to advance the distal array. Optionally, a marker is provided on the handle so that the deployment of the proximal and/or distal array can be visually determined.
The first and second electrode arrays will typically comprise a plurality of single electrode elements, usually including at least three electrode elements, frequently including five or more electrode elements, and often including ten or more electrode elements. Electrode elements will usually be configured to diverge and in come cases evert from the shaft in a simple curve having a generally constant radius as the electrode advances. Usually, the distal tips of each electrode will be circumferentially spaced-apart by equal distances, although some variation in spacing may be acceptable. The construction and configuration of the electrode elements is described in detail in U.S. Pat. No. 6,050,992, the full disclosure of which is incorporated herein by reference.
Once deployed, the electrode arrays will span a planar area which is disposed generally transverse to the axis of the shaft. The planar area which is spanned will be generally circular, typically having an area in the range from 3 cm2 to 20 cm2 (when the electrodes are fully deployed), often in the range from 3 cm2 to 15 cm2, and preferably in the range from 6 cm2 to 13 cm2. The areas of the first and second electrode arrays will usually be approximately equal, though that is not necessarily the case at all times. In some instances, it may be desirable to use electrode arrays having differing diameters and planar areas in order to produce lesions having different geometries. It will be appreciated that spaced-apart, axially aligned electrode arrays having circular peripheries with identical diameters will produce generally cylindrical lesions, while arrays having different diameters will produce lesions having conical sections.
Preferably, the first and second electrode arrays will be spaced-apart along an axial line therebetween, usually through the shaft. Preferably, the arrays are spaced-apart by distance in the range from 2 cm to 10 cm, usually from 3 cm to 7 cm, and preferably from 4cm to 6 cm.
The resulting volumes of necrosed tissue will generally be larger than those achievable with a single array device, such as the prior LeVeen(trademark) Needle Electrode discussed above. The treatment volumes achievable with the present invention may be at least 30 cm3 or larger, often being 70 cm3 or larger, sometimes being 150 cm3 or larger, and typically being in the range from 50 cm3 to 70 cm3.
In other preferred embodiments of the apparatus of the present invention, the first and second electrode arrays will be electrically isolated from each other in order to permit bipolar energization, i.e., to allow each electrode array to be separately connected as individual poles to an electrosurgical, radiofrequency, or other power supply. Such embodiments will typically include separate connectors for each of the electrode arrays in order to permit bipolar connection and operation. Of course, such separately connectable electrode arrays can also be operated individually in combination with a separate dispersive electrode, either externally mounted or internally mounted, as described for example, in copending application no. 09/656,307 (attorney docket no. 16807-002300), the full disclosure of which is incorporated herein by reference. In other embodiments, the first and second electrode arrays may be electrically coupled to permit common monopolar operation, although such monopolar operation will generally be less desirable. The first and second electrode arrays may be coupled internally, i.e., within the electrode deployment device itself, or externally, e.g., in the power supply and/or in the cable(s) connecting the electrode deployment device to the power supply.
In still other preferred embodiments, at least the first electrode array will include a first axial conductor extending proximally along the shaft from the first electrode array. The first axial conductor will be electrically coupled to the first electrode array so that they will operate at the same electrical potential. Usually, the second electrode array will also include an electrically coupled axial conductor which extends distally along the probe shaft. The first and second axial conductors will thus be opposed (as are the first and second electrode arrays). A gap will remain between the termini of the axial conductors to maintain electrical isolation between the first and second electrode arrays. Usually, the gap will be in the range from 0.5 cm to 5 cm, preferably from 1 cm to 3 cm. Typically, arrays having smaller diameters will require less spacing in order to maintain isolation, thus requiring smaller gaps. At least the first axial conductor will preferably extend axially in the proximal direction beyond the tips of the electrodes of the first array. Usually, if a second axial conductor is employed, its tip will extend axially in a distal direction beyond the tips of the electrodes of the array. Thus, in an exemplary embodiment, the tips of both axial conductors will be closer to each other than the tips of the electrodes in the respective electrode arrays.
In another aspect of the present invention, methods for treating a treatment region in tissue comprise deploying a first electrode array in tissue on one side of the treatment region. A second electrode array is deployed in tissue along an axis with the first array and on the other side of the treatment region. Both the first and second electrode arrays have concave sides and convex sides, and a concave side of the first array faces a concave side of the second array when the electrodes are fully deployed. After deploying the electrodes, an electrical current, usually a bipolar radiofrequency current, is applied from the first and second electrode arrays through the intervening tissue.
Usually, deploying the first electrode array comprises introducing a first probe through tissue to a location on one side of the treatment region and advancing a first plurality of at least three electrodes from the probe in an everting pattern. The second electrode array is deployed similarly by advancing a second plurality of at least three electrodes from the probe in an everting pattern at a location on the other side (typically opposite) of the treatment region. In the exemplary embodiments, the second electrode array is deployed from the same probe as was the first electrode array. Alternatively, the second electrode array may be deployed from a second probe through tissue to the location on the other side of the treatment region, e.g., the side opposite to the first electrode array.
The methods of the present invention are useful for treating a wide variety of tissues, particularly liver, lung, kidney, pancreas, stomach, spleen, uterus, and the like. Usually, the treatment region is a tumor or other diseased region and the treatment regions are imaged and identified using conventional techniques capable of elucidating a target tissue, such as ultrasonic scanning, magnetic resonance imaging (MRI), computer-assisted tomography (CT), fluoroscopy, nuclear scanning (using radiolabeled tumor-specific probes), and the like.
Tissue necrosis is preferably achieved by applying radiofrequency current in an amount and for a time sufficient to thermally destroy the tissue. Usually, the electrical current is applied at a frequency in the range from 300 kHz to 1.2 MHz. The current is applied at a power level selected to achieve the ablation, typically being in the range from 20 W to 300 W, usually from 50 W to 200 W. In the exemplary embodiments, the electrical current is supplied from a radiofrequency power supply in a bipolar manner where the first and second electrode arrays are attached to opposite poles of the power supply.
The methods of the present invention will preferably employ first and second electrode arrays having the dimensions set forth above with respect to the probes of the present invention and will preferably produce lesions having the volumes defined by probes, as set forth above.
Preferably, the methods will employ a first electrode array having a first axial conductor extending at least part of the way toward the second electrode array along an axis therebetween. The first axial conductor will be electrically coupled to the first electrode array and will terminate at a point located axially beyond the termination points of the electrode wires in the first electrode array, typically by a distance in the range from 5 mm to 10 mm. Such extension of the first axial conductor axially beyond the first electrode array, places the conductor closer to the second electrode array and optional second axial conductor. Thus, a preferred central electrical conduction path is provided between the first and second arrays. Usually, the second electrode array will also include a second axial conductor extending part of the way to the first array, and the second axial conductor will usually extend axially beyond the tips of the electrodes in the second electrode array. Thus, in a preferred embodiment, the proximal ends of the first axial conductors and the distal ends of the second axial conductors will lie closer to each other than will any of the tips of the individual electrodes in the two respective electrode arrays. Such a structure will provide a preferred electrical conduction path through a gap left between the termini of the first and second axial conductors. The current path and resulting current flux between the first and the second arrays is thus concentrated initially within the center of the tissue volume being treated (i.e., along the axis between the two arrays) which would not be the case in the absence of the axial conductors.
It has been further found that the use of the preferred everting electrodes in the first and second arrays defines a generally ovoid lesion volume generally bounded by an outer cylindrical wall having hemispherical ends. Use of the axial conductors along the axis between those arrays helps to assure that tissue in the center of the treatment region is treated before the tissues lying at the outer cylindrical and hemispherical peripheries of the treatment region is treated. After the central portions of the treatment region have been heated and necrosed to the extent that impedance to current flow increases, the individual electrodes of the electrode arrays will continue to heat and treat the outer portions. This two-step approach helps to assure that the entire volume, including both inner and outer portions of the treatment volume, is adequately necrosed.
Preferential heating of the center of the lesion can also reduce the effect of non-uniform blood flow at different points within the region to be treated. Destruction of the blood vessels within the center of the treatment region of tissue will tend to reduce perfusion differences in the larger, outer shell of the region. Moreover, even if the two electrode arrays experience different cooling because of such differences in blood flow, the everted configuration of the two opposed electrode arrays will enhance creation of a substantially contiguous shell surrounding the preferentially heated core. This effect further reduces the non-uniformities created by differential cooling which has been a major problem in prior efforts to treat large tissue volumes with bipolar radiofrequency ablation.
In a further aspect of the present invention, methods for bipolar radiofrequency necrosis of the tissue comprise deploying a first array of electrodes and a second array of electrodes in tissue. The first electrode array is deployed on one side of a treatment region and includes both a transverse face and an axial conductor extending in an axial direction from the transverse face. Usually, the electrode array which is located distally, i.e., furthest away from the entry point, will be deployed first in order to permit unimpeded imaging of the target tissue and the electrode during deployment. For that reason, the use of devices having separately deployable electrode arrays will often be preferred. Similarly, the second electrode array includes a transverse face and an axial conductor extending in an axial direction opposed to the first axial conductor on the first electrode array. Bipolar radiofrequency current is then applied between the two electrode arrays to heat and necrose tissue therebetween. The first and second electrode arrays will preferably have concave surfaces and fully everted electrode tips which face each other, but the use of such concave electrode arrays is not necessary. For example, the electrode arrays may be radially divergent, but not actually evert. Alternatively, the electrode arrays may be deployed by using a diverter to turn straight electrodes radially outward, as generally described in German patent application 2124684 to Stadelmayr.
The transverse faces of the first and second electrode arrays are preferably introduced from a single probe, but optionally could be introduced using two separate probes, such as two separate LeVeen(trademark) Needle Electrodes as described previously. The LeVeen(trademark) Needle Electrodes would have to be modified to include the axial conductors, as described in more detail below.
The tissues to be treated and the treatment conditions will be generally the same as described above in connection with the earlier embodiments of the methods of the present invention. Similarly, the electrode array dimensions will generally be the same as described above, except that the electrodes need not be concave or everting in all embodiments.
The present invention still further comprises kits including one or more probes capable of deploying at least first and second electrode arrays, generally as described above. The kits will further include instructions for use for deploying the electrode arrays and applying bipolar radiofrequency current for treating a tumor or other diseased condition within a target body tissue. The method set forth in the instructions for use will generally be in accord with any of the methods described above for the present invention. Usually, the treatment probe will be packaged in a conventional medical device package, such as a tray, box, tube, pouch, or the like. The instructions for use may be provided on a separate sheet of paper or may be printed in whole or in part on a portion of the packaging.